That’s great, but when you leave school, let’s hope you’ve got more to guide you than the Mr Ps of this world. Mr P is fine when it come to pedagogical grammars, but beyond that…
Yes, the world of English is very enormous, and people use it quite freely in real life (sometimes too freely), but truly speaking, I still prefer to use English the way it is used in schools (here I mean schools in English speaking countries)
Many can say I’m conservative and old-fashioned but anyway, I still think however English may develop, original features should be kept to make her remain… English 
(by the way, though I’m only 18, I’m of classical style :D)
Again that’s your choice, but believe me, if your school teacher and the Mr Ps tell you to always use “whom” even in the company of native-English speakers who now use “who” (which is quite a substantial amount of speakers, BTW) then, from those “who over whom” users, you’ll most likely face the same “I wonder why she didn’t say…” as you would from Mr Ps pedantic friends.
Flexibility, true knowledge of, and sensitivity to, appropriate language in its social context, will allow you to call yourself a proficient or expert user one day. The rest is all limitation brought about by too much focus on the, so called, standard dialect/sociolect. My advice, go for bidialectalism, at least.
Hi Nessie
If you have a teacher who tells you, for example, that ‘the lacking of’ is a typical and standard expression in English, then you might want to look for a better teacher. 
.
Hi, Amy
Actually, non-native teachers, even with years of experience in the field, make gaffes. For instance, our company hired a Russian English teacher to ascertain our language skills. And while speaking to us in English, she said “How do you call that”, though, as I understand, you don’t really say that, you’d rather say “What do you call that”.
the problem is that in Russian we would nevetheless use “how”, not what.
You’re welcome!
MrP
Steady on, old chap. We’re discussing “the solution for” versus “the solution to”, not who was responsible for World War II. (And I haven’t even mentioned “whom”.)
If you disagree with my explanation, simply post your counter-explanation. You’re perfectly free to do so.
MrP
Even if Nessie were studying EAP?
Don’t you love explanations that end with a doom-ridden warning? I find them quite funny, if somewhat out-of-touch.
[color=red]No choice! Amy, no choice!
=> 
Hard to believe this, Alex, but have any of your non-native teachers ever called wind power or solar power “continual energy” instead of “renewable energy”? Or have they ever given the answer “She’s the woman next to the door” to the question “Who did you talk to yesterday?” (Instead of “She’s the women next door”)
:D:D:D
(I hate to reveal these things, but there are more which are… more ridiculous) Should I laugh or cry? (No idea!)
But you’ve spotted their mistakes; which in itself deserves a .
MrP
which in itself deserves a .
==>> sorry but what do you mean, MrP? 
Hello Nessie,
The Free Dictionary puts it quite well:
All the best,
MrP